A significant problem that has been faced in many forms of imaging technology is termed halation. This image quality diminishing phenomenon is caused by the reflection of actinic radiation which has passed through the radiation sensitive medium and struck a supporting surface in the imageable article. The reflected radiation then passes through the sensitive medium again, imaging the article in a pattern not faithful to the original exposing light pattern. This causes a reduced faithfulness in the final image.
One traditional way of reducing halation is to provide a radiation-absorbing characteristic in the supporting surface. Dye layers, carbon black layers and the like have often been used for this purpose. The use of such radiation-absorbing, antihalation layers means that the imageable article and often the imaged article will have the color of the radiation-absorbing material of the support surface. Bleachable dyes or strippable layers are often used to allow that undesirable color contribution to be removed. That approach requires considerable manual labor and design expertise to work even moderately well and increases the cost of manufacturing the film by adding layers and coating steps.
It is generally known that ultraviolet (UV) radiation and near ultraviolet (near UV) radiation tend to be the most culpable ranges of radiation with respect to halation. The use of titania-filled or coated substrates tends to greatly reduce that problem. Titania provides a clean white background and effectively absorbs much of the radiation below 380 nm. The use of titania still does not solve the problem of near UV halation (i.e., radiation between 390-480). That problem is significant in the reproduction of visible images.